Plasticity and damage in aluminum syntactic foams deformed under dynamic and quasi-static conditions

Syntactic foams were fabricated by liquid metal infiltration of commercially pure and 7075 aluminum into preforms of hollow ceramic microspheres. The foams exhibited peak strengths during quasi-static compression ranging from -100 to -230 MPa, while dynamic compression loading showed a 10-30% increase in peak strength magnitude, with strain rate sensitivities similar to those of aluminum-matrix composite materials. X-ray tomographic investigation of the post-compression loaded foam microstructures revealed sharp differences in deformation modes, with the unalloyed-Al foam failing initially by matrix deformation, while the alloy-matrix foams failed more abruptly through the formation of sharp crush bands oriented at about 45° to the compression axis. These foams displayed pronounced energy-absorbing capabilities, suggesting their potential use in packaging applications or for impact protection; proper tailoring of matrix and microsphere strengths would result in optimized syntactic foam properties.